摘要:

A review of the energy/load situation before 1939 shows that, as regards technical progress in the transmission field, the needs of the time were satisfied.The present energy famine makes necessary the development of new resources, some of which are remotely situated. The authors suggest that in these circumstances transmission by direct current can be of service. They ask interested parties to consider the possibilities carefully and to make an early decision for or against. The position in many countries, in particular in some of those belonging to the British Commonwealth, demands laboratory research and field experiment, sponsored in or from Britain. Possible research projects are briefly discussed. The paper includes an outline of a major transmission project in each of four Continents.

DOI:10.1049/pi-2.1949.0072

出版商:IEE    

年代:1949

数据来源: IET

摘要:

The requirement for digital computing machines of large storage capacity has led to the development of a storage system in which the digits are represented by a charge pattern on the screen of a cathode-ray tube. Initial tests have been confined to commercial tubes. Short-term memory of the order of 0.2 sec is provided by the insulating properties of the screen material. Long-term memory is obtained by regenerating the charge pattern at a frequency greater than 5 c/s. The regeneration makes accurate stabilization of the position of the charge pattern on the c. r. tube unnecessary. The properties required of a storage system, and its operation as part of a machine, are stated. If such a machine were operated in the series mode, an instruction would be set up and obeyed in 600 μsec.

DOI:10.1049/pi-2.1949.0078

出版商:IEE    

年代:1949

数据来源: IET

摘要:

There are three methods in general use for driving pumps in water-works, namely by steam-, Diesel- or electrically-operated machinery. It is the purpose of the present paper to compare the costs of such plant for each of six typical waterworks loads. An outline of the duties to be discussed is first given, with notes on the various kinds of machinery suitable. The method of arriving at the capital charges, with diagrams showing the cost of pumping units is next shown, and thereafter, the means of calculating the running expenses. The estimated annual charges are then set out in tabular form, followed by some notes on the results obtained. Appendices are included which provide an estimate of the costs of a heat pump for a pumping station; a demonstration of the losses caused by the rotor-resistance method of speed variation in pumping sets, indicating that such means of control can be economic; and finally an explanation for the need of standby generating plant in pumping stations.

DOI:10.1049/pi-2.1949.0081

出版商:IEE    

年代:1949

数据来源: IET

摘要:

The paper deals with polyphase commutator machines, treated as a single subject, and shows how all the different types can be classified and analysed within a common theoretical framework.The classification is made into three general groups depending on the construction of the machines, namely the shunt and series motors, the commutator frequency changer and the Scherbius machine. The second group includes the well-known Schrage variable-speed motor, and the third group includes many types of speed-regulating machines and phase advancers. After discussing this classification, the paper describes the practical arrangement of each type of machine and the associated regulating apparatus, and explains the general effect on performance. It is shown that two curves, the speed/torque curve and the current-locus curve, tell all that it is required to know about the performance of a machine.In the theoretical analysis an even greater unity of treatment is possible. The paper shows that the theory of all the important types of polyphase commutator machines can be derived from that of a slip-ring induction motor which has a slip-frequency voltage injected into the secondary winding. The vector diagrams and equations of the principal types are developed by this method; the equations check with those derived by other methods.The chief differences between the three groups are brought out in the characteristics. Families of speed/torque and current-locus curves are shown and compared for some of the principal types.

DOI:10.1049/pi-2.1949.0087

出版商:IEE    

年代:1949

数据来源: IET

摘要:

High-intensity high-pressure mercury-vapour (h.p.m.v.) lamps are now being used in cinema studios and for other important applications. During the development of lamps and circuits suitable for these purposes, it was necessary to solve circuit difficulties of a rather special nature, and it is the purpose of the paper to discuss these problems. Fairly complete descriptions are also given of some of the circuits which experience has shown to be suitable for commercial use. Although most of the lamps towards which the discussion is directed are of the high-pressure mercury-vapour type, the principles are often of much wider interest and application.

DOI:10.1049/pi-2.1949.0092

出版商:IEE    

年代:1949

数据来源: IET

摘要:

Interest in the study of surge-voltage distribution in transformers has been stimulated by the increasing attention given to the impulse strength of transformers. Experimental methods of investigating surge phenomena necessitate the use of the cathode-ray oscillograph, and for transformer work the recurrent-surge oscillograph method has important advantages. As low voltages are used there is no risk of damage to the transformer. The recurring trace is peculiarly suitable for visual observation and eliminates most of the difficulties associated with single transient recording.This paper assesses the value of the recurrent-surge oscillograph for transformer investigations and deals briefly with its development and design. A description is given of the latest E.R.A. instrument, which incorporates some special features.Methods of applying the recurrent-surge oscillograph to transformers are discussed, and its position with regard to transformer research is reviewed principally with reference to the work of the Electrical Research Association.

DOI:10.1049/pi-2.1949.0094

出版商:IEE    

年代:1949

数据来源: IET

摘要:

The paper briefly mentions earlier instruments of the type indicated by the title and goes on to describe a fully automatic oscillograph in which 15 cathode-ray tubes, housed in a common camera, may be photographed side by side on a common 70-mm film. The equipment is normally quiescent, and the cathode-ray tubes are blacked out, but any abrupt change of the supply voltage influences a detector which initiates the cathode beams and starts a film-driving motor. Recording is effective right from the outset of the system disturbance, as an electronic sweep of the cathode-ray beams anticipates, and merges into, the mechanical acceleration of the film. On selected elements, time-delay networks provide signal storage, enabling events preceding the disturbance by about 1 millisec to be included in the records. A code number for the date and time of each operation is marked against the corresponding record. The equipment is capable of giving detailed service records of modern high-speed switchgear and protective equipment.

DOI:10.1049/pi-2.1949.0095

出版商:IEE    

年代:1949

数据来源: IET

摘要:

Sections 2–6 give a summary of the available knowledge of surge phenomena and for convenience of treatment this is divided into five parts; lightning and lightning surges, surge propagation, distribution of surge voltages in inductive apparatus, effects of surges on insulation and surge protective devices.The first part of this indicates the importance of lightning-current measurements and specifies the various types of lightning surge which can occur on overhead lines. The second part draws attention to those aspects of surge propagation which are important in relation to the protection of substation apparatus, with special emphasis on the protection afforded by attenuation by corona. The third part discusses the problem of designing transformers to withstand surges and refers to the question of surge testing. The fourth part gives a summary of the available data on the surge strength of relief gaps, line insulators and cables. The fifth part summarizes the characteristics of recognized protective devices.The summary of available knowledge is followed by specific recommendations for its application to the protection of various types of overhead transmission line and of substation.Finally, attention is drawn to the need for further research, and suggestions for new researches or extensions of existing researches are made.

DOI:10.1049/pi-2.1949.0099

出版商:IEE    

年代:1949

数据来源: IET

摘要:

This paper describes a simple way of making a sub-standard resistor, of value about one ohm, suitable for use at frequencies up to about 10 Mc/s and having substantial current-carrying capacity. In essence it is a revival of bifilar flat-strip construction in contrast to a bifilar of round wire, a method which was commercially used at low frequencies but did not achieve popularity. A bifilar strip of Eureka, 2 mils thick, is separated by a thin mica leaf and clamped tightly between clamping boards of brass or Keramot. It is shown that the time-constant of the assembly depends only on the thickness of the strips and of the mica leaf. The calculated time-constant is 10−8sec. The resistor was developed primarily for the purpose of obtaining an oscillogram of pulses of current which were substantially rectangular in shape and lasting about 15 microsec, the p.d. across the resistor being displayed on the screen of a cathode-ray tube. The effect of the capacitance between the strips is examined analytically, and the capacitance correction to the impedance is found to be about 0.5% at 10 Mc/s, when the length of the bifilar is 50 cm.It is pointed out that the resistor, combined with a valve voltmeter, provides a simple way of checking the calibration of ammeters at frequencies up to about 5 Mc/s.The construction is very robust and so simple that it can readily be made to suit the requirements of each particular application as it arises. It is intended mainly for use as a test-bed tool rather than as an adjunct to a high-precision standard bridge.

DOI:10.1049/pi-2.1949.0103

出版商:IEE    

年代:1949

数据来源: IET

摘要:

The mode of operation of a simple transductor connection is described. The influence of the different properties of the iron core upon the mode of operation and the characteristics of the transductor is discussed and the requirements are formulated. A practical figure of merit is proposed.

DOI:10.1049/pi-2.1949.0105

出版商:IEE    

年代:1949

数据来源: IET